Rotatable object with positive lock and means to unlock and rotate said object

ABSTRACT

A positive lock rotating linkage comprising a supporting structure, a first segment mounted for rotation on the supporting structure and upon which is secured an object to be rotated by a predetermined angle, and means for locking the first segment at each extreme position of its angular motion. A second segment is mounted for rotation coaxially and independently of the first segment and such second segment includes means for unlocking the first segment and for subsequently rotating the first segment through the above-mentioned predetermined angle.

United States Patent 1191 Leuenberger ROTATABLE OBJECT WITH POSITIVE LOCK AND MEANS TO UNLOCK AND ROTATE SAID OBJECT [75] Inventor: Urs Leuenberger, Fontevrault,

Quebec, Canada [73] Assignee: Canada Wire and Cable Limited,

Toronto, Ontario, Canada 22 Filed: Apr. 16, 1973 21 App]. No.: 351,597

[52] U.S. Cl. 46/78, 74/99 R [51] Int. Cl. A63h 27/00 [58] Field of Search 74/107, 103, 102, 99 R,

74/99 A, 497; 46/76, 77, 78; 244/102 R, 102 SL [56] References Cited UNITED STATES PATENTS 501,926 7/1893 Douglass 74/102 2,551,788 5/1951 Cameron 46/78 2,591,344 4/1952 Elliott 74/102 X 2,645,882 7/1953 Cook 46/77 2,962,908 12/1960 Landau et a1 74/99 1 51 Feb. 11, 1975 3,186,245 6/1965 Bowman et al. 74/107 X 3,212,350 10/1965 Bradford 74/102 X 3,752,421 8/1973 Harvey et al. 46/77 FOREIGN PATENTS OR APPLICATIONS 526,872 9/1940 Great Britain 244/102 OTHER PUBLICATIONS Merry pg. 1158 of Vol. 10, No. 8 of IBM Technical Disclosure Bulletin, Jan. 1968.

Primary Examiner-F. Barry Shay [57] ABSTRACT A positive lock rotating linkage comprising a supporting structure, a first segment mounted for rotation on the supporting structure and upon which is secured an object to be rotated by a predetermined angle, and means for locking the first segment at each extreme position of its angular motion. A second segment is mounted for rotation coaxially and independently of the first segment and such second segment includes means for unlocking the first segment and for subsequently rotating the first segment through the abovementioned predetermined angle.

12 Claims, 9 Drawing Figures sum 1 or a PATENTED FEB! I I975 PATENIED FEB! 1 I975 SHEET 30F 3 ROTATABLE OBJECT WITH POSITIVE LOCK AND MEANS TO UNLOCK AND ROTATE SAID OBJECT BACKGROUND OF THE INVENTION This invention relates to a positive lock rotating linkage for rotating an object through a predetermined angle and which locks itself at each extreme position of its travel, and is particularly suited to the operation of retractable landing gears of radio-controlled model aircrafts.

Several known linkages are used for operating retractable landing gears of model aircrafts, although all of them have serious failings.

One known linkage is operated in the downward direction of the landing gear by a gas under pressure and .in the upward direction by the action of a compression spring. This mechanism is provided with a positive mechanical lock in the down position of the gear but this positive lock is maintained only as long as the pressure is maintained. A modification of the above mechanism is also known in which the linkage is operated in both directions by pneumatic pressure. This device has the disadvantage that no positive lock is provided in either direction and can collapse if pneumatic pressure is lost. Another additional disadvantage of the pneumatically operated linkages is that the speed of operation thereof depends on the pneumatic pressure, and varies as the pneumatic pressure varies. It cannot be independently controlled.

Another known linkage is operated by a mechanical arm which is connected to a locking segment. This mechanism has the disadvantage that a positive lock is only maintained as long as the operating mechanical arm is held in an exact position in either extreme of the two directions of motion. This mechanism may therefore unlock itself by vibrations caused by noise in the servo system driving the operating arm, or by strong mechanical shocks caused by hard impact. It has the additional disadvantage that impulse forces on the ro tating segment are completely absorbed by the locking segment which is connected to the operating mechanical arm, and this locking segment is subject to failure.

Another known linkage has integral electric motors in each unit. The motor drives through a gear train and jack screw to operate the linkage. This device has a positive lock in the sense that the jack screw cannot rotate unless the electric motor is operated. It has the disadvantage that limit switches are required at each end of the linkage motion and these switches can result in high frequency electrical noise, which causes radio interference.

Several other types of mechanical linkages are known, but each of these has one or more of the shortcomings listed in the above examples.

SUMMARY OF THE INVENTION It is therefore the object of the present invention to provide a mechanical linkage which overcomes the above drawbacks and more particularly which provides a positive lock at each extreme position of its travel even if pneumatic pressure is lost, which is independent of the exact positioning of the actuating arm and thus may not unlock itself by vibrations, and which is more reliable than the known linkages.

The positive lock rotating linkage, in accordance with the invention, comprises a supporting structure,

and a first segment mounted for rotation on such supporting structure and upon which is secured an object to be rotated by a predetermined angle, such as the struts of the landing gears of a model aircraft. Means are provided for locking the first segment at each extreme position of its angular motion and a second segment is mounted for rotation coaxially and independently of the first segment. Such second segment is provided with means for unlocking the first segment and for subsequently rotating the first segment through such predetermined angle.

The first segment may be of arcuate shape and means for locking the first segment at each extreme position of its angular motion may include a spring secured to the supporting structure and having an end portion biassed against the arcuate surface of the first segment, and a groove in the first segment at a location corresponding to each extreme position of its angular movement and into which the end portion of the spring is adapted to drop to lock the rotating linkage. However, it is to be understood that other types of locking devices, such as a spring loaded pin, may be used.

The means for unlocking the first segment and for subsequently rotating it through such predetermined angle may include first means for raising the end portion of the spring from the groove in the first segment so as to unlock the first segment, and second means for subsequently engaging stops provided on the first segment so as to rotate the first segment through such predetermined angle.

In one specific embodiment of the invention, the second segment subtends an arc which is substantially less than the arc subtented by the first segment and includes an arcuate portion of the same radius as the first segment. The means for raising the end portion of the spring is a ramp on the second segment extending downwardly from both ends of the arcuate portion. The above arrangement is such as to permit a certain amount of free movement of the second segment with respect to the first segment so as to render the first segment independent of the exact positioning of the second segment in the lock position. It is to be understood however that the invention is not limited to this particular embodiment and that other arrangements may also be envisaged.

In a prefered embodiment of the invention, the second segment is rotated by means of an hydraulic motor including a cylinder pivotally mounted at one end on the supporting structure and a piston protruding through the other end of the cylinder and connected to the second segment for rotating such second segment through the desired angle when the piston is displaced in the cylinder. With the specific structure of the second segment disclosed above, the angle of rotation obtained with a linear hydraulic motor may be anywhere between 45 and However, it is to be understood that a rotary motor could be used and such an arrangement would permit an angular motion varying from 45 to 315.

The supporting structure may be a U-shaped channel and the first and the second segments as well as the cylinder could be mounted on shafts extending through the walls of such U-shaped channel and the spring secured to the base of the channel.

In a specific application of the rotating linkage in accordance with the invention, the object to be rotated may be the struts of the landing gear of a model aircraft. Such struts may be secured to the first segment of the linkage. In a specific embodiment of the invention, the struts are bent at approximately 90 and the end thereof opposite the wheels of the model aircraft form the shaft which extends through the walls of the U-shaped channel and support the first and second segments.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be disclosed, by way of example, with reference to a preferred embodiment thereof and to the accompanying drawings in which:

FIG. 1 illustrates an end view of the positive lock rotating linkage in accordance with the invention, such end view being taken along line l-1 of FIG. 2;

FIG. 2 illustrates a side view of the positive lock rotating linkage with one sidewall thereof being removed;

FIG. 3 illustrates a section view of the rotating linkage taken along a line 33 of FIG. 2;

FIGS. 4 and 5 illustrate a side and plan view of the first segment of the rotating linkage, FIG. 5 being taken as indicated by line 5--5 of FIG. 4;

FIGS. 6 and 7 illustrate a side and elevation view respectively of the second segment of the rotating linkage, FIG. 7 being taken as illustrated by line 77 of FIG. 6; and

FIGS. 8 and 9 illustrate a side and plan view of an alternative embodiment of the first segment of FIGS. 4 and 5.

DESCRIPTION OF SPECIFIC EMBODIMENTS Referring to FIGS. l-3, there is shown an embodiment of a positive lock rotating linkage in accordance with the invention comprising a U-shaped channel 10 in which is mounted for rotation a shaft 12 which is integral with one end of the strut 14 of the landing gear of a model aircraft and having a wheel 16 rotatably mounted at its other end. A first segment 18 is locked on shaft 12 by means of screws 20 and provided with stops 21 adapted to be engaged by a second segment 22 rotatably mounted on shaft 12 and operated by an hydraulic motor 24. It is to be understood that other objects could be rotated with the linkage in accordance with the invention and that shaft 12 does not have to form part of such object. The shaft 12 may be fixed to the channel 10 and the object to be rotated secured to the segment 18 in any conventional way. A spacer 25 is provided on shaft 12 for filling the gap between the walls of channel 10.

Hydraulic motor 24 includes a cylinder 26 having a blind end 28 and a rod end 30. A piston 32 is movable inside cylinder 26 by means of fluid fed through ports 34 and 36. The piston 32 is connected to segment 22 by means of rod 38 and pin 40. The fluid fed through ports 34 or 36 moves piston 32 in one direction or the other and so rotates segment 22 a predetermined angle determined by the stroke of the piston. Hydraulic motor 24 may be operated by a closed circuit hydraulic control system such as described in US. patent application Ser. No. 351,596 entitled A Closed Circuit Hydraulic Control filed Apr. 16, 1973, although it is to be understood that a conventional hydraulic control system may be used. The cylinder 26 is pivotally mounted at its blind end to a shaft 42 passing through channel 10. Spacers 44 and 46 are used to position the cylinder 26 on the shaft so that its piston rod 38 is properly aligned with respect to pin 40.

A spring 48 is secured to channel 10 by any suitable means such as rivets 50 and has a bent end portion 52 which protrudes through the channel 10 and is adapted to engage grooves 54 in the segment 18.

Segment 18 which is illustrated in greater detail in FIGS. 4 and 5 comprises a cylindrical portion 180 and an arcuate portion 18b. Cylindrical portion 18a may be secured to shaft 12 by screw 20, as mentioned previously, which is inserted into threaded aperture 56. As to arcuate portion 18b, it is provided, as mentioned previously, with grooves 54 and with stops 21, adapted to be engaged by segment 22 during rotation of such segment.

Segment 22, which is illustrated more clearly in FIGS. 6 and 7, comprises a cylindrical portion 22a and an arcuate portion 22b which is of the same radius as the arcuate portion 18b of segment 18. The arcuate portion 22b is provided with a hole 58 for receiving pin 40 as mentioned previously and with two ramps 60 which are adapted to contact the end portion 52 of spring 48 to raise the end portion 52 out of groove 54 in the first segment 18 upon rotation of segment 22. The ramps 60 are preferably designed so that the rate of lifting of the locking spring per unit of angular rotation of the segment is a constant. However, this is not an essential aspect of the present invention.

The positive lock rotating linkage so far described operates as follows:

Assuming that the segment 18 is locked in the position illustrated in FIG. 1 of the drawings, fluid pressure is applied through port 36 to push piston 32 towards the rod end 30 of the cylinder 26. Rod 38 rotates segment 22 counterclockwise to cause ramp 60 to lift the end portion 52 of spring 48 out of slot 54 in segment 18. Segment 22 then contacts stop 21 of segment 18 and drives segment 18 and shaft 12 until the end of the stroke of piston 32. At that point the end portion 52 of spring 48 should fall in the groove 54 located at the other end of the segment 18 and lock the segment in position. The reverse action is brought about by the piston rod 38 moving the segment 22 in the reverse direction. The segment 22 has a second ramp 60 which raises the end portion 52 of the locking spring 48 out of groove 54 in the segment 18 and causes the segment 18 to rotate in the reverse direction. This rotation continues until the locking spring 48 again falls into its groove in the segment 18.

In the example of the present embodiment, strut 14 which is secured to segment 18 is rotated through an angle of and, consequently, the angle between the two grooves 54 of arcuate portion 180 of segment 18 must be 90 as illustrated in FIG. 5. In addition, the stops 21 on arcuate portion 18a of segment 18 must be located at such a distance apart or must have an angular pitch such that the end portion52 of spring 48 is completely out of groove 54 before the segment 22 contacts the stop 21. It will be understood that the stroke of piston 32 must be sufficient to provide the 90 angular motion of segment 18 plus the angular displacement necessary to move the end portion of spring 48 out of grooves 54.

It has been found in practice that the arrangement illustrated in FIGS. 1-7 using a linear hydraulic motor may rotate an object through any angle in a range varying from 45 to The lower limit is imposed by the structure of segment 22 whereas the upper limit is due to the hydraulic motor which, obviously, cannot effectively rotate the segment 22 more than a certain angle which is substantially less than 180.

In a particular application such as the one mentioned above, it may be very important from a weight point of view to make the U-shaped channel, the rotating segments, the hydraulic motor and the spacers from lightweight materials such as aluminum, zinc or plastic.

Although the invention has been disclosed with reference to a preferred embodiment thereof, it is to be understood that many variations are envisaged within the scope of the present invention. For example, the angle of rotation of the segment 18 can be anywhere between 45 and 135 using a linear hydraulic motor and between 45 and 315 using a rotary motor. Also, there are many alternatives for mounting the object to be rotated to the segment 18 other than using a portion of the strut 14 as a shaft and securing the segment 22 to the shaft by means of screws. For example, shaft 12 could be fixed to the walls of the U-shaped channel and the strut 14 could be inserted into a hole 62 in segment 18, as illustrated in FIGS. 8 and 9 and locked in position by collar 64. The shape of the segment 18 as well as the form of the stops 21 may also be modified. For example, the segment 18 could be provided with ears 66 for ensuring that the end portion 52 of the spring 48 will not slip pass the slot 54 at the end of travel of segment 18.

Many options are also available for attaching the rod 38 to the segment 22. Also several alternate designs .could be used instead of spring 48 for locking segment 18, such as, for example, a spring-loaded pin. Finally, the invention is in no way limited to the use of a U- shaped channel for mounting the rotating linkage. Any type of mounting arrangement may be used.

What is claimed is:

1. A positive lock rotating linkage comprising:

a. a supporting structure;

b. a first segment, means mounting said first segment for rotation on said supporting structure, and an object secured on said first segment to be rotated back and forth by a predetermined angle;

c. means located on said supporting structure for locking said first segment at each extreme position of its angular motion against angular rotation in both directions; and

d. a second segment, means mounting said second segment for rotation on said supporting structure coaxially and independently of said first segment, said second segment including means for coacting with said locking means to unlock said first segment at each extreme position of its angular motion and for subsequently rotating said first segment through said predetermined angle, said segments being constructed and arranged to allow said second segment a predetermined amount of free angular motion relative to said first segment before unlocking the first segment and subsequently rotating said first segment at each extreme position of its angular motion so as to render said first segment independent of the exact positioning of said second segment in the lock position.

2. A positive lock rotating linkage as defined in claim 1, wherein said first segment is of arcuate shape and wherein said means for locking said first segment at each extreme position of its angular motion includes a spring secured to said supporting structure and having an end portion biassed against the arcuate surface of said first segment, and a groove in said first segment at a location corresponding to each extreme position of its angular movement and into which the end portion of said spring is adapted to drop to lock the rotating linkage.

3. A positive lock rotating linkage as defined in claim 2, wherein said first segment has stops thereon and wherein said means for unlocking said first segment and for subsequently rotating said first segment through said predetermined angle includes first means for raising the end portion of said spring from the groove in said first segment so as to unlock said first segment, and second means for subsequently engaging the stops of the first segment so as to rotate the first segment through said predetermined angle.

4. A positive lock rotating linkage as defined in claim 3, wherein said second segment subtends an are which is substantially less than the arc subtended by said first segment, and including an arcuate portion of the same radius as said first segment, and wherein said first means for raising the end portion of said spring is a ramp on said second segment extending downwardly from both ends of the arcuate portion thereof, such arrangement permitting said free movement of said second segment with respect to said first segment so as to render said first segment independent of the exact positioning of said second segment in the lock position.

5. A positive lock rotating linkage as defined in claim 4, wherein said ramp is designed so that the rate of lifting of the spring per unit angular rotation of the second segment is a constant.

6. A positive lock rotating linkage as defined in claim 1, further comprising means for rotating said second segment through said predetermined angle.

7. A positive lock rotating linkage as defined in claim 6, wherein said means for rotating said second segment is an hydraulic motor including a cylinder pivotally mounted on said supporting structure and a piston pro truding through the other end of said cylinder and connected to said second segment for rotating said second segment through said predetermined angle when said piston is displaced in said cylinder.

8. A positive lock rotating linkage as defined in claim 7, wherein the angle of rotation of said first segment is between 45 and 135.

9. A positive lock rotating linkage as defined in claim 8, wherein said angle of rotation is 10. A positive lock rotating linkage as defined in claim 7, wherein said supporting structure is a U- shaped channel and wherein said first and second segments are mounted on a first shaft extending through the walls of said U-shaped channel at one end thereof whereas said cylinder is mounted on a second shaft extending through the walls of said U-shaped channel at the other end thereof.

11. A positive lock rotating linkage as defined in claim 10, wherein the object to be rotated is a strut and wheel of a model aircraft, and wherein said strut supports said wheel and is bent at approximately 90 at the end thereof opposite the wheel and forms the first shaft which extends through the walls of the U-shaped channel and upon which the first and second segments are mounted, said first segment being secured to said first shaft whereas said second segment is pivotally mounted thereon.

12. A positive lock rotating linkage as defined in claim 10, wherein the object to be rotated is a strut and wheel of a model aircraft, and wherein said strut supports said wheel and is secured to said first segment at the end thereof opposite the wheel, said first shaft being secured to the U-shaped channel and said first and second segments being rotatably mounted on said first shaft. 

1. A positive lock rotating linkage comprising: a. a supporting structure; b. a first segment, means mounting said first segment for rotation on said supporting structure, and an object secured on said first segment to be rotated back and forth by a predetermined angle; c. means located on said supporting structure for locking said first segment at each extreme position of its angular motion against angular rotation in both directions; and d. a second segment, means mounting said second segment for rotation on said supporting structure coaxially and independently of said first segment, said second segment including means for coacting with said locking means to unlock said first segment at each extreme position of its angular motion and for subsequently rotating said first segment through said predetermined angle, said segments being constructed and arranged to allow said second segment a predetermined amount of free angular motion relative to said first segment before unlocking the first segment and subsequently rotating said first segment at each extreme position of its angular motion so as to render said first segment independent of the exact positioning of said second segment in the lock position.
 2. A positive lock rotating linkage as defined in claim 1, wherein said first segment is of arcuate shape and wherein said means for locking said first segment at each extreme position of its angular motion includes a spring secured to said supporting structure and having an end portion biassed against the arcuate surface of said first segment, and a groove in said first segment at a location corresponding to each extreme position of its angular movement and into which the end portion of said spring is adapted to drop to lock the rotating linkage.
 3. A positive lock rotating linkage as defined in claim 2, wherein said first segment has stops thereon and wherein said means for unlocking said first segment and for subsequently rotating said first segment through said predetermined angle includes first means for raising the end portion of said spring from the groove in said first segment so as to unlock said first segment, and second means for subsequently engaging the stops of the first segment so as to rotate the first segment through said predetermined angle.
 4. A positive lock rotating linkage as defined in claim 3, wherein said second segment subtends an arc which is substantially less than the arc subtended by said first segment, and including an arcuate portion of the same radius as said first segment, and wherein said first means for raising the end portion of said spring is a ramp on said second segment extending downwardly from both ends of the arcuate portion thereof, such arrangement permitting said free movement of said second segment with respect to said first segment so as to render said first segment independent of the exact positioning of said second segment in the lock position.
 5. A positive lock rotating linkage as defined in claim 4, wherein said ramp is designed so that the rate of lifting of the spring per unit angular rotation of the second segment is a constant.
 6. A positive lock rotating linkage as defined in Claim 1, further comprising means for rotating said second segment through said predetermined angle.
 7. A positive lock rotating linkage as defined in claim 6, wherein said means for rotating said second segment is an hydraulic motor including a cylinder pivotally mounted on said supporting structure and a piston protruding through the other end of said cylinder and connected to said second segment for rotating said second segment through said predetermined angle when said piston is displaced in said cylinder.
 8. A positive lock rotating linkage as defined in claim 7, wherein the angle of rotation of said first segment is between 45* and 135*.
 9. A positive lock rotating linkage as defined in claim 8, wherein said angle of rotation is 90*.
 10. A positive lock rotating linkage as defined in claim 7, wherein said supporting structure is a U-shaped channel and wherein said first and second segments are mounted on a first shaft extending through the walls of said U-shaped channel at one end thereof whereas said cylinder is mounted on a second shaft extending through the walls of said U-shaped channel at the other end thereof.
 11. A positive lock rotating linkage as defined in claim 10, wherein the object to be rotated is a strut and wheel of a model aircraft, and wherein said strut supports said wheel and is bent at approximately 90* at the end thereof opposite the wheel and forms the first shaft which extends through the walls of the U-shaped channel and upon which the first and second segments are mounted, said first segment being secured to said first shaft whereas said second segment is pivotally mounted thereon.
 12. A positive lock rotating linkage as defined in claim 10, wherein the object to be rotated is a strut and wheel of a model aircraft, and wherein said strut supports said wheel and is secured to said first segment at the end thereof opposite the wheel, said first shaft being secured to the U-shaped channel and said first and second segments being rotatably mounted on said first shaft. 